The human heart is the muscle that is responsible for pumping blood throughout the vascular network. Veins are vessels that carry blood toward the heart while arteries carry blood away from the heart. The human heart consists of two atrial chambers and two ventricular chambers. Atrial chambers receive blood from the body and the ventricular chambers, which include larger muscular walls, pump blood from the heart. A septum separates the left and the right sides of the heart.
Various devices and methods have been utilized to assist the heart in blood circulation, particularly for patients having congestive heart failure (commonly referred to as heart disease), which is a condition that results in any structural or functional cardiac disorder that impairs the ability of the heart to fill with or pump blood throughout the body. These devices generally include a pump, which may reside in a subcutaneous pump pocket, and cannulae fluidically attaching the pump to the vascular network. One cannula is used to transmit oxygenated blood from the left side of the heart to the pump; another cannula is used to direct that blood from the pump to the arterial network.
Despite the benefits gained by assisting the heart with the implantable pump, issues may arise from the presence of the cannula within the vessel. The arteries and veins of the vascular network have a particular anatomical structure that includes three layers: the tunica externa, the tunica media, and the tunica intima, respectively from the outer most layer, inward. The tunica intima, which includes a combination of endothelial cells and the protein elastin, creates a biological barrier that performs several functions. One essential function is the maintenance of a smooth inner surface that resists clotting and promotes smooth blood flow. The endothelial cells secrete various regulatory compounds that aid processes, such as vasoregulation and coagulation. When a conventional cannula is positioned within a blood vessel, the polymer or urethane comprising the cannula, or the mere presence of the cannula itself, may physically and/or chemically perturb the endothelial cells of the tunica intima and induce a prothrombotic environment. Thrombus formations may wash into the implantable pump of the assist device causing pump failure or alternatively induce a thrombolic event, including stroke or kidney infarct. Accordingly, it would be beneficial to create an environment within the cannula that mimics the native biological structure and framework of the blood vessel to reduce the occurrence of thrombic events.